1. Field of the Invention
The present invention pertains to corrugated shipping cartons and, in particular, to corrugated shipping cartons having tear strips and the like for dividing the shipping carton into two portions, one of which is particularly suitable for display purposes.
2. Brief Description of the Prior Art
In many retail stores today, goods shipped in corrugated cartons are conveniently set up for display by removing an upper portion, leaving a tray-like container holding some or all of the goods shipped in the carton. While it is a relatively simple operation to sever a corrugated cardboard shipping carton with a knife to form a display tray, this operation presents a risk of injury to a person cutting the box and to the goods inside if the depth of the cut is not accurately controlled. Further, during a cutting operation, the knife blade tends to wander from side to side, leaving a non-uniform wavy or ragged edge with detracts from the appearance of the display tray so formed.
For these and other reasons, there is a demand for easy opening shipping cartons having a tear string, tear tape, or other tear strip which, when pulled through the outer wall of a shipping carton performs the desired severing operation. For example, U.S. Pat. No. 3,884,348 discloses a corrugated cardboard shipping carton having a tear strip located along medial walls of the carton for severing them to provide a display container. In order to minimize strain on the tear strip, and to more accurately control tearing, the outer wall of the shipping carton is perforated along the path of tearing, on either side of the tear strip. This arrangement, however, requires reinforcing construction to minimize strain on the perforations tending to induce unintentional severing of the shipping carton prior to arrival at its destination point or prior to its intended display.
Another arrangement for minimizing the strain when severing with a tear strip, is given in U.S. Pat. No. 3,727,750, which is directed to a sterile package for medical products and the like. The tear strip disclosed therein is formed as a portion of a laminated outer wall of the paper board package. The tear strip is defined by dual pairs of score lines in the inner and outer surfaces of the paperboard package. To prevent the intrusion of unwanted materials into the package through the score lines and to provide an easy opening tearing operation, pulling on the tear strip causes a delamination between inner and outer sets of score lines formed on the inner and outer laminations, respectively. This construction suffers from the same disadvantages pointed out above, namely, the score lines introduce a weakening in the package. A similar arrangement of dual pairs of scorelines on opposing surfaces of a shipping carton are given in U.S. Pat. No. 3,502,257. The arrangement differs from that preceding, in that a single layer of cardboard forms the outer wall.
Pairs of weakening lines are also present in the tray-forming container of U.S. Pat. No. 3,276,666. The weakening lines herein are formed on the inside liner or surface of the corrugated container material. Several steps are taken in order to induce the desired weakening effect. For example, the weakened lines are interrupted at intervals and a reinforcing tape is attached to the outside liner of the container, which also assists in providing an even tearing. The tear strip, formed between weakening lines, as a portion of the inner liner, is pulled through the outer liner of the carton. The weakening along parallel spaced-apart lines on the inner liner of the container decreases container strength.
In order to provide shipping containers of greater strength and containers having a generally tubular appearance, U.S. Pat. No. 3,873,017 provides a triple-walled polygonal construction. A tear strip is provided between the middle and outer layers adjacent one end of the container to provide access to the interior thereof. This construction is, in general, not well suited for forming a display device.
In addition to cardboard shipping containers, pull strips, pull strings or the like are found in a variety of different types of packages. For example, U.S. Pat. No. 4,093,069 discloses a cardboard envelope surrounding a stack of sheet materials. Interfitting half portions of the envelope, when mated, form an enclosed interior. A tear strip, preferably with a row of perforations is provided in the cardboard envelope to provide easy tearing in a direction generally transverse to a seam joining the two portions.
At times, it is desired to reuse the container in which goods are shipped. U.S. Pat. No. 4,621,736 provides a reclosable paperboard carton having a tear string attached to an inside liner of the carton wall. The tear string, when drawn through the carton wall, divides the carton into a lid and a container portion. The container portion, when squeezed at its open end, allows interfitting within the lid portion to thereby provide a reclosing feature. To assist in severing the two carton portions, partial cuts are made in the outside liner of the carton material, a feature which, as pointed out above, weakens the strength of the carton. As an alternative to the tear string, the inside liner of the carton material may be cut along a pair of spaced, parallel lines to thereby form a tear strip from the inner liner material, in a manner similar to that described above.
In addition to rectangular or polygonal cardboard shipping containers. tear strings and the like are frequently found in cylindrical container bodies for frozen juice concentrate and the like. As a first example, U.S. Pat. No. 3,409,206 provides an improvement in the pull-strip tearing of one end of a cylindrical paper body by forming the cylindrical body from specially fabricated overlapping paper layers having fibers which are aligned relative to the direction of tearing. The fibers, aligned in an overlapping relationship, are oriented such that pulling of the tear strip causes an upstream fiber to pick up its neighboring overlying downstream fiber. The tearing is assisted by lines of weakness in both inner and outer wall surfaces of the paper wall. A second example of this general type of container is shown in U.S. Pat. No. 3,402,876, which assists the tearing operation by providing an enlarged pull tab which is generally formed separately from the container wall. A perforated line of weakness assists in the tearing. This container, as well as other containers for fruit juice concentrate and other liquid materials, typically requires a lamination of a variety of materials, the inner lamination layer typically providing a liquid-tight barrier of plastic, foil, or the like non-paper material. Corrugated cardboards, in general, are not employed in containers of this type.
Some containers are so fragile that they do not require lines of weakness formed by perforation, slits or the like, in the container material to guide or assist in reducing the effort required to pull a tear strip. For example, U.S. Pat. No. 3,343,747 is directed to a cellophane outer wrapper for soft cigarette packs. Tear strips, generally formed of plastic, are secured to the cellophane wrapper with adhesive. Since the cellophane offers minimal resistance to tearing, no weakening lines are required.